Exophthalmos in a horse resulting from an adenocarcinoma of the frontal sinus.

This research study documents the case of a fifteen-year-old thoroughbred horse exhibiting eyeball protrusion which was caused by an adenocarcinoma (cancer) in the left frontal sinus.

Overview of the Case

• A fifteen-year-old thoroughbred gelding presented with a medical condition identified as exophthalmos in his left eye. Exophthalmos, often known as eyeball protrusion or bulging eyes, is a symptom where the eyeball moves out from the eye socket.
• The cause of this condition was initially unknown until post-death examination, also called a necropsy, was performed.

Findings from the Necropsy

• The necropsy revealed that the horse had an adenocarcinoma of the left frontal sinus. An adenocarcinoma is a type of cancerous tumor originating from glandular tissue. In this case, it developed in the left frontal sinus, one of the air spaces located in the forehead region of the skull.
• This tumor led to the noted exophthalmos by expanding towards the back (caudally) through a thin, sieve-like structure in the skull called the cribriform plate. The cribriform plate separates the brain from the nasal cavity, and its breach by the tumor indicated an advanced level of the disease.
• Upon reaching the orbit (the eye socket), the growing tumor displaced the horse’s eyeball pushing it forward (anteriorly), which resulted in the observable exophthalmos.

Implications of the Study

• This study presents a crucial evidence of exophthalmos in horses being a symptom of an underlying severe health issue, such as an adenocarcinoma in the frontal sinus.
• Findings from the necropsy underscore the importance of thorough veterinary examinations when unusual symptoms, like eyeball protrusion, are observed. These symptoms could be signaling the presence of life-threatening conditions.
• This case study might also strengthen the veterinary practice in addressing similar cases in the future, and enhance the understanding of tumor development, its progression and resulting symptoms in horses.